This invention relates to a thermal insulating article prepared by covering a mat made of inorganic fibers such as glass wool or rock wool, with a film coat along an entire surface including upper and lower surfaces, lateral sides and front and rear sides, and also relates to a method of manufacturing such a thermal insulating article.
According to prior arts, thermal insulating articles made of inorganic fibers such as those of glass wool or rock wool have a stimulating itchy effect specific to such fibers, so that they are normally covered with a film coat in order to eliminate such a stimulating effect and also prevent the degradation of the thermal insulating article due to dew condensation.
However, in the case of prior thermal insulating article xe2x80x9cAxe2x80x9d covered with such a film coat as disclosed in Japanese Patent No. 2,820,641, the mat is not covered with the outer film coat at the lateral sides xe2x80x9cBxe2x80x9d as shown in FIG. 8 of the accompanying drawings, so that it can give rise to an unpleasantly stimulating itchy effect by fine fibers scattered from those sides.
Japanese Patent Laid-Open Nos. 53-39067 and 6-79849 and Japanese Utility Model Laid Open No. 52-162710 disclose techniques for covering a mat of inorganic fibers with a film coat along the entire surface including the upper and lower surfaces, the lateral sides and the front and rear sides. Coated mats according to the above described patent are normally compressed for packaging for the purpose of improving the efficiency of packing and packaging. Thus, the film coat is perforated to discharge or release air in the inside, and/or the end lugs binding the opposite edges of the film coat is made apt to aerate in order to quickly discharge air from the inside of the mat, to prevent the film coat from being torn by bursting air at the time of compressing and packaging, and to make air quickly flow into the inside to expand the mat after unpacking.
More specifically, Japanese Patent Laid-Open No. 53-96076 discloses means for manufacturing a thermal insulating article having a predetermined length, wherein mats of the above described type having an appropriate thickness and a predetermined length are constantly moved on a line at regular intervals, while covering them by a film from above and below in a continuous operation, and heating and fusing the upper film and the lower film for bonding along the lateral sides and also at the front and rear ends of each mat at appropriate respective positions on the line. Then, the fused areas of the film are cut along the center line thereof to produce thermal insulating articles having the predetermined length.
According to Japanese Patent Laid-Open No. 6-79849, mats typically made of glass wool and thermoplastic resin film are fed simultaneously, and the film is partly heated and fused for bonding along the front and rear edges of each mat as viewed in the feeding direction. Subsequently the film is cut along the thermally fused and bonded areas, and partly torn apart along the feeding direction in the areas that are not thermally fused, so that consequently the film show a predetermined length for each mat. Then, the pieces of film cut apart are used to cover the lateral sides and the front and rear sides of the mat to complete the process of forming a thermal insulating article.
A mat according to either of the above patent documents are accompanied by the following problems.
Firstly, referring to FIG. 2 of the accompanying drawings, excessive film corresponding to the sealing length L1 is required for the film to sufficiently cover the front and rear ends of the mat, so that the film cost rises as a function of the length L1 in the manufacturing process. In other words, the sealing length L1 has to be reduced to suppress the film cost and hence the manufacturing cost, although no means is proposed for cost reduction.
FIG. 3 of the accompanying drawings schematically illustrates the mat and the film covering the upper and lower surfaces of the mat. If the length W of the end lugs is too long, it would be pinched by and/or entangled by the packaging machine in the compression/packaging process, to interfere with and stop the operation of the machine, and to reduce the efficiency of the operation. Additionally, the end lugs would extend to the outside of the installation frame for containing the thermal insulating article, so that the extended part of the film may have to be cut, to increase the work load and prolong the installing operation.
If the compressed and packaged thermal insulating article is used for thermal insulation and sound absorption, it is normally compressed to a size equal to xc2xd to {fraction (1/10)} of the size provided in JIS (Japanese Industrial Standards) for packaging. Then, the compressed thermal insulating article has to be made to restore the size conforming to JIS.
If the sealing length L1 is reduced to dissolve the first problem, the upper film and the lower film would be peeled off from each other along bonded areas due to the resilient force of the compressed mat.
If the sealing length L1 is reduced by compressing the mat between the front and rear ends, to make it smaller than the size defined by JIS before covering it with film, the film tension would be raised to press the mat, so that the mat would not restore the original size to meet the dimensional requirement of JIS.
Finally, since the film is thermally fused and bonded while compressing the mat by the tension of the film, the bonding areas of the film would be laterally displaced by the film tension, so that the bonding of the film would not be satisfactory and/or the film would be torn. While these problems may be eliminated by using a thick film, such a film will by turn raise the manufacturing cost.
In view of the above identified problems of the prior art, it is therefore an object of the present invention to provide a thermal insulating article that is completely covered by a film coat along the entire surface thereof to meet the requirements of the applicable standards in terms of structure, strength and so on and still can be manufactured and installed efficiently at low cost. Another object of the present invention is to provide a method of manufacturing such thermal insulating articles in a continuous way.
According to the present invention, the above objects and other objects of the invention are achieved by providing a thermal insulating article comprising a rectangularly parallelepipedic mat of an aggregate of inorganic fibers, a synthetic resin upper surface film and a synthetic resin lower surface film; wherein
said upper surface film covers an upper surface of said mat, is bent to extend to a lower surface of the mat along lateral surfaces of the mat, and is bonded to the lower surface film along edge lugs;
said upper surface film is bent to extend to the lower surface along front and rear surfaces of the mat, and is bonded to the lower surface film; characterized in that
said mat comprises a front end section, a rear end section and a central section;
said mat with the upper surface film is pressed downwardly at the front and rear end sections by a predetermined depth;
the front end surface, the rear end surface and the upper surface of the mat are covered by the upper surface film which has a sum of a length for covering the upper surface of the mat, a length to be used for being bonded to the lower surface film and a marginal length produced by reducing the thickness of the mat at the front and rear end sections; and
said mat has a predetermined thickness at the central section.
In another aspect of the present invention, there is also provided a method of manufacturing a thermal insulating article comprising a mat of inorganic fibers, an upper surface film bonded to an upper surface of the mat and a lower surface film bonded to a lower surface of the mat, said upper surface film and said lower surface film being bonded to each other along edge lugs and end lugs of the thermal insulating article; said method comprising steps of:
forming a continuous source mat of inorganic fibers having a predetermined density and a predetermined thickness by means of a drying machine;
forming rectangularly parallelepipedic unit mats by cutting the continuous mat to a predetermined length;
feeding unit mats intermittently so as to make adjacent mats show an interval therebetween by regulating switching time of a stopper, the interval being sum of a length of the upper surface film necessary for it to cover the oppositely disposed end surfaces of the adjacent mats and a length of the upper surface film necessary for it to be bonded to the lower surface film;
covering the upper surface of each mat by the upper surface film by bonding the upper surface film to the upper surface of the mat, and also covering the lower surface of the mat by bonding the lower surface film to the lower surface of the mat;
bonding the upper surface film and the lower surface film along the edge lugs;
causing the mat to pass through a sag absorbing section, and feeding it to a sealing machine;
stopping the mat at a time of alignment of a center position of the interval of adjacent mats and a center of said sealing machine;
compressing the rear end section of a mat and the front end section of the adjacent mat to a predetermined thickness, and maintaining the compression;
pressing the upper surface film downwardly between the rear end section of a mat and the front end section of the adjacent mat, to contact the upper surface film to the lower surface film along the rear end surface of a mat and the front end surface of the adjacent mat;
bonding the upper surface film and the lower surface film near the rear end surface of a mat and the front end surface of the adjacent mat; and
cutting the upper surface film and the lower surface film at said center position, to form the thermal insulating article.